Richter Scale. Advance

Transcription

1 Richter Scale Lesson Concept Link Seismographs determine the magnitude of an earthquake by measuring its force and duration. This is reported on a Richter Scale that increases by powers of ten. Lesson 6.9 demonstrated how observable phenomena are used to determine the intensity of earthquakes Richter Scale clarifies how earthquakes reported on Richter Scales indicate increasing each number by ten times the previous. The scales link to lesson 6.11 where damage to structures is explored. Time 55 minutes Materials Advance Preparation Procedure: Engage Whole class 2 lb Package of spaghetti Individual H1 Richter Scale handout H2 Richter Scale Worksheet Resources R1 Damage picture R2 Damage picture R3 Richter Scale Worksheet Answer Key 1. Purchase and count out spaghetti bundles for demonstration. 2. Duplicate student copies of handout H1 and H2. 3. Review resources pictures at the end of the lesson and load on powerpoint on doc camera to use in step Read through the lesson and decide if moment magnitude information will be added for your class. (10 minutes) The severity of an earthquake can be expressed in terms of magnitude. Magnitude is related to the amount of seismic energy released at the epicenter of the earthquake. 1. Display two pictures of damage caused by an earthquake at a 5.5 and a 6.7 on the Richter Scale. Ask students to talk to a partner about the increase in damage between just two numbers? Why do you think a 6.7 earthquake is so much greater than a 5.5? How much damage might a 7.5 earthquake cause? Chart student ideas. S cience M atters 1

2 Explore (5 min.) The difference between numbers on the Richter Scale is ten times the previous number. This increase is exponential. 2. Distribute bundles of spaghetti to each set of partners. 3. Hold up one piece the spaghetti. Bend the piece between your hands until it breaks. Label this a 1 on the Pasta Magnitude scale. 4. Hold up a bundle of 10 pieces of spaghetti. Bend the bundle until it breaks. Notice the difference in effort it takes to break the bundle. If the pasta magnitude scale were like the earthquake magnitude scale this would be a Pasta Magnitude of 2 break. 5. Hold up 100 pieces of pasta, the remainder of the package. Bend the bundle until it breaks. Notice the work it takes to break the bundle. This is a Pasta Magnitude 3 break. 6. Lead a class discussion including these questions: Explain a. In this model what does the spaghetti represent? (The earth, rocks, tectonic plates b. What do your hands represent? (Forces, stress, another plate) c. What does the breaking spaghetti represent? (An earthquake) (10 minutes) Scientists can measure the amount of energy an earthquake releases using different scales 7. The magnitude scales for earthquakes are logarithmic scales. The Richter scale is based on seismograph readings measuring Earth movement. Each increase in whole numbers represents a 10-fold increase in ground shaking. So, during a magnitude 6 quake, the ground shakes 10 times as much as during a magnitude 5 quake. How does the model of spaghetti help us understand the difference between each number? Teacher Note: In addition to the Richter Scale, scientists also use a Moment Magnitude that measures the total energy of an earthquake, called the seismic moment. The seismic moment of an earthquake is determined based on three factors. The first factor is the distance that rock slides along a fault surface after it breaks, called the fault slip. The second factor is the area of the fault surface that is actually broken by the earthquake. And the third factor is the measurement of how rigid the rocks are near the broken fault. A strong rock, such as granite, cannot be broken easily. That makes it a highly rigid rock. When an earthquake happens, stations with advanced seismology tools all take readings of the fault slip, the fault area, and the rigidity. Those readings are sent to central locations. Seismologists multiply the fault slip, fault area, and rigidity together to determine the actual seismic moment. Explain (20 minutes) Scales such as Richter can be compared to models that increase such as time. 8. Ask students to review the Richter Scale Worksheet. What do you notice about what is used to show the difference between numbers on the Richter. Does it use pasta or something else? S cience M atters 2

3 9. Ask students to discuss how to complete the worksheet with a partner. Share out some ideas. 10. Ask students to complete the Richter Scale Worksheet by calculating the total number of seconds each level would represent. Teacher Note: Students may have difficulty comparing the Richter scale to a time scale. Explain to the students that scaling or making comparisons is often done to help understand a concept (such as the odds of winning a lottery being greater than being struck by lightening, or if the earth was the size of a softball, the sun would be the size of a normal-sized classroom). The time periods given are approximate. If a level one on the Richter scale is 1 second, a level three would be 1*10*10 = 102 = 100 seconds or 1 minute and 40 seconds. Have students calculate the exact time knowing that there are 60 seconds in a minute, 60 minutes in an hour. Students can be allowed to use calculators. Evaluate (10 minutes) 11. After students finish the Richter Scale handout, ask them to partner with another student to check their work. 12. Ask students to explain how the model of time or pasta helps understand the change in magnitude between each number on the Richter Scale. (Complete prompt in notebooks) S cience M atters 3

4 S cience M atters 4 H1

5 S cience M atters 5 H2

6 R1 Chino Hills Earthquake 2008 Magnitude 5.5 S cience M atters 6

7 R2 Northridge Earthquake Magnitude 6.7 S cience M atters 7

8 S cience M atters 8 R3